The
CPC and the contributors to the Forecast Forum caution potential users of
this predictive information that they can expect only modest skill.

ENSO
Alert System Status: La
Niña Advisory

Outlook:

La Niña
is
expected to last at least into the Northern Hemisphere spring 2011.

Discussion:

During
November 2010, the ongoing La Niña was reflected by below-average sea surface
temperatures (SSTs) across the equatorial Pacific Ocean (Fig. T18).The
Niño SST index values were between –1.3°C to–1.6°C for the month (Table T2).The subsurface oceanic heat content (average temperatures in the upper
300m of the ocean) also remained well below-average in association with a
shallower-than-average thermocline across the central and eastern equatorial
Pacific (Fig. T17).Convection
remained enhanced over Indonesia and suppressed over the western and central
equatorial Pacific (Fig. T25).Enhanced low-level easterly
trade winds and anomalous upper-level westerly winds continued over the
equatorial Pacific (Figs. T20, T21).Collectively,
these oceanic and atmospheric anomalies reflect a moderate-to-strong La Niña.

Consistent
with nearly all ENSO forecast models (Figs.
F1-F13), La Niña is
expected to peak during November-January and to continue into the Northern
Hemisphere spring 2011.Thereafter,
the fate of La Niña is more uncertain.The
majority of forecast models and all of the multi-model combinations (thicker
lines) indicate a return to ENSO-neutral conditions during the Northern
Hemisphere spring and early summer.However,
a smaller number of models, including the NCEP Climate Forecast System, suggest
that La Niña could persist into the summer.Historically, there are more multi-year La Niña episodes than El Niño
episodes, but other than support from a few model runs, there is no consensus
for a multi-year La Niña at this time.Consequently,
La Niña is anticipated to continue into the Northern Hemisphere spring, with no
particular outcome favored thereafter.